Ivlyth/Readme.md

## Readme.md

      
    Raw
  

              Readme.md
            
          
    Cascades

Session Basics

Using Passive Deletes

Contextual/Thread-local Sessions

Managing Transactions

delete-orphan(from stackoverflow)

Object Relational Tutorial

Association Object

Keep going ...

  
## s1.py
# !/usr/bin/env python
# -*- coding:utf8 -*-
'''
Author : myth
Date   : 14-8-11
Email  : belongmyth at 163.com
'''

import sys

reload(sys)
sys.setdefaultencoding(u'utf-8')

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, scoped_session
from sqlalchemy import Column, ForeignKey, INTEGER, VARCHAR, DATETIME, FLOAT, BOOLEAN, TEXT
from sqlalchemy.orm import relationship, backref

from datetime import datetime, timedelta
import random
import math

# 数据库配置
_db_config = {
    u'db_type': u'mysql',
    u'db_driven': u'mysqldb',
    u'db_user': u'root',
    u'db_passwd': u'bmw12345',
    u'db_host': u'localhost',
    u'db_port': u'3306',
    u'db_selected_db': u'salearn',
    u'db_charset': 'utf8'
}

_db_connect_params = u'%(db_type)s+%(db_driven)s://%(db_user)s:%(db_passwd)s@%(db_host)s/%(db_selected_db)s?charset=%(db_charset)s'

DB_CONNECT_PARAMS = _db_connect_params % _db_config

#DB_CONNECT_PARAMS='mysql+mysqldb://root:root@localhost/account?charset=utf8'
u'''
    :param pool_size=5: the number of connections to keep open
        inside the connection pool. This used with
        :class:`~sqlalchemy.pool.QueuePool` as
        well as :class:`~sqlalchemy.pool.SingletonThreadPool`.  With
        :class:`~sqlalchemy.pool.QueuePool`, a ``pool_size`` setting
        of 0 indicates no limit; to disable pooling, set ``poolclass`` to
        :class:`~sqlalchemy.pool.NullPool` instead.

    :param pool_recycle=-1: this setting causes the pool to recycle
        connections after the given number of seconds has passed. It
        defaults to -1, or no timeout. For example, setting to 3600
        means connections will be recycled after one hour. Note that
        MySQL in particular will disconnect automatically if no
        activity is detected on a connection for eight hours (although
        this is configurable with the MySQLDB connection itself and the
        server configuration as well).
'''
engine = create_engine(DB_CONNECT_PARAMS, echo=True, pool_size=10, pool_recycle=3600)

Session = sessionmaker(bind=engine)
ScopedSession = scoped_session(sessionmaker(bind=engine))


def get_session():
    return ScopedSession()


def get_no_scoped_session():
    return Session()

#DBSession = get_session()

BaseModel = declarative_base(bind=engine)

#BaseModel.objects = DBSession.query_property()  # all model will have it
BaseModel.__table_args__ = {  # 指定所有model的默认参数
                              u'mysql_charset': u'utf8',
                              u'mysql_engine': u'InnoDB'
}


def create_tables():
    BaseModel.metadata.create_all(engine)


def drop_tables():
    BaseModel.metadata.drop_all(engine)


u'''
学生成绩管理系统

班级表

学生表

科目表

成绩表

涉及操作:
  添加/修改/删除班级
  添加/修改/删除学生
  添加/修改/删除科目
  添加/修改/删除学生成绩

'''


class MClass(BaseModel):
    __tablename__ = u'mclass'  #数据库表名称

    id = Column(u'id', INTEGER, primary_key=True)  #班级ID
    name = Column(u'name', VARCHAR(50), unique=True, nullable=False)  #班级名称,唯一且不能为空
    created = Column(u'created', DATETIME, default=datetime.now)

    def __repr__(self):
        return u'<Class %s with %d students, created at %s>' % (
            self.name, len(self.students), self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MStudent(BaseModel):
    __tablename__ = u'mstudent'

    id = Column(u'id', INTEGER, primary_key=True)  #学生ID
    class_id = Column(u'class_id', ForeignKey(MClass.id), nullable=False)  #学生所属班级ID
    name = Column(u'name', VARCHAR(30), nullable=False)  #学生名称,必填
    age = Column(u'age', INTEGER)  #学生年龄， 选填
    created = Column(u'created', DATETIME, default=datetime.now)

    cls = relationship(MClass, backref=backref(u'students', cascade=u'all'))  #学生所属班级对象

    def __repr__(self):
        return u'<Student %s in Class %s, created at %s>' % (
            self.name, self.cls.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MCourse(BaseModel):
    __tablename__ = u'mcourse'

    id = Column(u'id', INTEGER, primary_key=True)  #课程ID
    name = Column(u'name', VARCHAR(30), unique=True, nullable=False)  #课程名称,唯一且非空
    created = Column(u'created', DATETIME, default=datetime.now)

    def __repr__(self):
        return u'<Course %s, created at %s>' % (self.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MScore(BaseModel):
    __tablename__ = u'mscore'

    id = Column(u'id', INTEGER, primary_key=True)  #成绩记录ID
    student_id = Column(u'student_id', ForeignKey(MStudent.id), nullable=False)  #学生ID
    course_id = Column(u'course_id', ForeignKey(MCourse.id), nullable=False)  #课程ID
    score = Column(u'score', FLOAT, default=0.0)

    student = relationship(MStudent, backref=backref(u'scores', cascade=u'all'))
    course = relationship(MCourse, backref=backref(u'scores', cascade=u'all'))

    def __repr__(self):
        return u'<Student %s in Class %s with %.1f for Course %s, created at %s>' % (
            self.student.name, self.student.cls.name, self.score, self.course.name,
            self.created.strftime(u'%Y-%m-%d %H:%M:%S')
        )


cls = MClass
stu = MStudent
c = MCourse
s = MScore


class RandomException(Exception):
    pass


def random_exception():
    if random.random() < 0.0000005:
        raise RandomException()


def random_age():
    return random.randint(20, 30)


def random_score():
    return round(random.random() * 100, 1)


def init_data():
    session = get_session()
    try:
        course_names = [u'语文', u'数学', u'英语']
        courses = []
        # 创建3门课程
        for course_name in course_names:
            course = MCourse()
            course.name = course_name
            random_exception()
            session.add(course)
            courses.append(course)

        # 随机创建3个班级
        for cls_index in range(3):
            # create a class
            cls = MClass()
            cls.name = u'class-%d' % (cls_index + 1, )
            random_exception()

            # 为每个班级随机创建10个学生
            for stu_index in range(10):
                student = MStudent()
                student.name = u'class-%d-student-%d' % (cls_index + 1, stu_index + 1)
                student.age = random_age()
                random_exception()

                # 为每个班级中的学生随机生成每门课程的成绩
                for course in courses:
                    score = MScore()
                    score.score = random_score()
                    score.student = student
                    score.course = course
                    random_exception()
                    #session.add(score)

                #session.add(student)
                cls.students.append(student)

            session.add(cls)

        session.commit()
        return True
    except RandomException:
        print u'random exception happened, rollback all transaction'
        session.rollback()
    finally:
        session.close()
    return False


def random_delete_class():
    session = get_session()
    classes = session.query(MClass).all()
    cls = random.choice(classes)
    print u'will delete class %s with id %d' % (cls.name, cls.id)
    session.delete(cls)
    session.commit()


def random_delete_student():
    session = get_session()
    students = session.query(MStudent).all()
    stu = random.choice(students)
    print u'will delete student %s with id %d' % (stu.name, stu.id)
    session.delete(stu)
    session.commit()


def random_delete_course():
    session = get_session()
    courses = session.query(MCourse).all()
    course = random.choice(courses)
    print u'will delete course %s with id %d' % (course.name, course.id)
    session.delete(course)
    session.commit()


def main():
    # 删除所有的表
    print u'dropping tables ...'
    drop_tables()
    # 创建所有的表
    print u'creating tables ...'
    create_tables()
    # 初始化数据
    print u'init database records ...'
    init_success = init_data()
    if init_success:
        # 随机操作数据
        print u'random delete class ...', u'*' * 50
        random_delete_class()
        print u'random delete student', u'*' * 50
        random_delete_student()
        print u'random delete course', u'*' * 50
        random_delete_course()


if __name__ == u'__main__':
    main()

## s2.py
# !/usr/bin/env python
# -*- coding:utf8 -*-
'''
Author : myth
Date   : 14-8-11
Email  : belongmyth at 163.com
'''

import sys

reload(sys)
sys.setdefaultencoding(u'utf-8')

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, scoped_session
from sqlalchemy import Column, ForeignKey, INTEGER, VARCHAR, DATETIME, FLOAT, BOOLEAN, TEXT
from sqlalchemy.orm import relationship, backref

from datetime import datetime, timedelta
import random
import math

# 数据库配置
_db_config = {
    u'db_type': u'mysql',
    u'db_driven': u'mysqldb',
    u'db_user': u'root',
    u'db_passwd': u'bmw12345',
    u'db_host': u'localhost',
    u'db_port': u'3306',
    u'db_selected_db': u'salearn',
    u'db_charset': 'utf8'
}

_db_connect_params = u'%(db_type)s+%(db_driven)s://%(db_user)s:%(db_passwd)s@%(db_host)s/%(db_selected_db)s?charset=%(db_charset)s'

DB_CONNECT_PARAMS = _db_connect_params % _db_config

#DB_CONNECT_PARAMS='mysql+mysqldb://root:root@localhost/account?charset=utf8'
u'''
    :param pool_size=5: the number of connections to keep open
        inside the connection pool. This used with
        :class:`~sqlalchemy.pool.QueuePool` as
        well as :class:`~sqlalchemy.pool.SingletonThreadPool`.  With
        :class:`~sqlalchemy.pool.QueuePool`, a ``pool_size`` setting
        of 0 indicates no limit; to disable pooling, set ``poolclass`` to
        :class:`~sqlalchemy.pool.NullPool` instead.

    :param pool_recycle=-1: this setting causes the pool to recycle
        connections after the given number of seconds has passed. It
        defaults to -1, or no timeout. For example, setting to 3600
        means connections will be recycled after one hour. Note that
        MySQL in particular will disconnect automatically if no
        activity is detected on a connection for eight hours (although
        this is configurable with the MySQLDB connection itself and the
        server configuration as well).
'''
engine = create_engine(DB_CONNECT_PARAMS, echo=True, pool_size=10, pool_recycle=3600)

Session = sessionmaker(bind=engine)
ScopedSession = scoped_session(sessionmaker(bind=engine))


def get_session():
    return ScopedSession()


def get_no_scoped_session():
    return Session()

#DBSession = get_session()

BaseModel = declarative_base(bind=engine)

#BaseModel.objects = DBSession.query_property()  # all model will have it
BaseModel.__table_args__ = {  # 指定所有model的默认参数
                              u'mysql_charset': u'utf8',
                              u'mysql_engine': u'InnoDB'
}


def create_tables():
    BaseModel.metadata.create_all(engine)


def drop_tables():
    BaseModel.metadata.drop_all(engine)


u'''
学生成绩管理系统

班级表

学生表

科目表

成绩表

涉及操作:
  添加/修改/删除班级
  添加/修改/删除学生
  添加/修改/删除科目
  添加/修改/删除学生成绩

'''


class MClass(BaseModel):
    __tablename__ = u'mclass'  #数据库表名称

    id = Column(u'id', INTEGER, primary_key=True)  #班级ID
    name = Column(u'name', VARCHAR(50), unique=True, nullable=False)  #班级名称,唯一且不能为空
    created = Column(u'created', DATETIME, default=datetime.now)

    students = relationship(u'MStudent', backref=backref(u'cls'), passive_deletes=True)  #学生所属班级对象

    def __repr__(self):
        return u'<Class %s with %d students, created at %s>' % (
            self.name, len(self.students), self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MStudent(BaseModel):
    __tablename__ = u'mstudent'

    id = Column(u'id', INTEGER, primary_key=True)  #学生ID
    class_id = Column(u'class_id', ForeignKey(MClass.id, ondelete=u'CASCADE'), nullable=False)  #学生所属班级ID
    name = Column(u'name', VARCHAR(30), nullable=False)  #学生名称,必填
    age = Column(u'age', INTEGER)  #学生年龄， 选填
    created = Column(u'created', DATETIME, default=datetime.now)

    # cls = relationship(u'MClass', backref=backref(u'students'), passive_deletes=True)  #学生所属班级对象
    scores = relationship(u'MScore', backref=backref(u'student'), passive_deletes=True)

    def __repr__(self):
        return u'<Student %s in Class %s, created at %s>' % (
            self.name, self.cls.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MCourse(BaseModel):
    __tablename__ = u'mcourse'

    id = Column(u'id', INTEGER, primary_key=True)  #课程ID
    name = Column(u'name', VARCHAR(30), unique=True, nullable=False)  #课程名称,唯一且非空
    created = Column(u'created', DATETIME, default=datetime.now)

    scores = relationship(u'MScore', backref=backref(u'course'), passive_deletes=True)

    def __repr__(self):
        return u'<Course %s, created at %s>' % (self.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


class MScore(BaseModel):
    __tablename__ = u'mscore'

    id = Column(u'id', INTEGER, primary_key=True)  #成绩记录ID
    student_id = Column(u'student_id', ForeignKey(MStudent.id, ondelete=u'CASCADE'), nullable=False)  #学生ID
    course_id = Column(u'course_id', ForeignKey(MCourse.id, ondelete=u'CASCADE'), nullable=False)  #课程ID
    score = Column(u'score', FLOAT, default=0.0)

    # course = relationship(u'MCourse', backref=backref(u'scores'), passive_deletes=True)
    # student = relationship(u'MStudent', backref=backref(u'scores'), passive_deletes=True)

    def __repr__(self):
        return u'<Student %s in Class %s with %.1f for Course %s, created at %s>' % (
            self.student.name, self.student.cls.name, self.score, self.course.name,
            self.created.strftime(u'%Y-%m-%d %H:%M:%S')
        )


cls = MClass
stu = MStudent
c = MCourse
s = MScore


class RandomException(Exception):
    pass


def random_exception():
    if random.random() < 0.0000005:
        raise RandomException()


def random_age():
    return random.randint(20, 30)


def random_score():
    return round(random.random() * 100, 1)


def init_data():
    session = get_session()
    try:
        course_names = [u'语文', u'数学', u'英语']
        courses = []
        # 创建3门课程
        for course_name in course_names:
            course = MCourse()
            course.name = course_name
            random_exception()
            session.add(course)
            courses.append(course)

        # 随机创建3个班级
        for cls_index in range(3):
            # create a class
            cls = MClass()
            cls.name = u'class-%d' % (cls_index + 1, )
            random_exception()

            # 为每个班级随机创建10个学生
            for stu_index in range(10):
                student = MStudent()
                student.name = u'class-%d-student-%d' % (cls_index + 1, stu_index + 1)
                student.age = random_age()
                random_exception()

                # 为每个班级中的学生随机生成每门课程的成绩
                for course in courses:
                    score = MScore()
                    score.score = random_score()
                    score.student = student
                    score.course = course
                    random_exception()
                    #session.add(score)

                #session.add(student)
                cls.students.append(student)

            session.add(cls)

        session.commit()
        return True
    except RandomException:
        print u'random exception happened, rollback all transaction'
        session.rollback()
    finally:
        session.close()
    return False


def random_delete_class():
    session = get_session()
    classes = session.query(MClass).all()
    cls = random.choice(classes)
    print u'will delete class %s with id %d' % (cls.name, cls.id)
    session.delete(cls)
    session.commit()


def random_delete_student():
    session = get_session()
    students = session.query(MStudent).all()
    stu = random.choice(students)
    print u'will delete student %s with id %d' % (stu.name, stu.id)
    session.delete(stu)
    session.commit()


def random_delete_course():
    session = get_session()
    courses = session.query(MCourse).all()
    course = random.choice(courses)
    print u'will delete course %s with id %d' % (course.name, course.id)
    session.delete(course)
    session.commit()


def main():
    # 删除所有的表
    print u'dropping tables ...', u'*' * 50
    drop_tables()
    # 创建所有的表
    print u'creating tables ...', u'*' * 50
    create_tables()
    # 初始化数据
    print u'init database records ...', u'*' * 50
    init_success = init_data()
    if init_success:
        # 随机操作数据
        print u'random delete class ...', u'*' * 50
        random_delete_class()
        print u'random delete student', u'*' * 50
        random_delete_student()
        print u'random delete course', u'*' * 50
        random_delete_course()


if __name__ == u'__main__':
    main()
	# !/usr/bin/env python
	# -- coding:utf8 --
	'''
	Author : myth
	Date : 14-8-11
	Email : belongmyth at 163.com
	'''

	import sys

	reload(sys)
	sys.setdefaultencoding(u'utf-8')

	from sqlalchemy import create_engine
	from sqlalchemy.ext.declarative import declarative_base
	from sqlalchemy.orm import sessionmaker, scoped_session
	from sqlalchemy import Column, ForeignKey, INTEGER, VARCHAR, DATETIME, FLOAT, BOOLEAN, TEXT
	from sqlalchemy.orm import relationship, backref

	from datetime import datetime, timedelta
	import random
	import math

	# 数据库配置
	_db_config = {
	u'db_type': u'mysql',
	u'db_driven': u'mysqldb',
	u'db_user': u'root',
	u'db_passwd': u'bmw12345',
	u'db_host': u'localhost',
	u'db_port': u'3306',
	u'db_selected_db': u'salearn',
	u'db_charset': 'utf8'
	}

	_db_connect_params = u'%(db_type)s+%(db_driven)s://%(db_user)s:%(db_passwd)s@%(db_host)s/%(db_selected_db)s?charset=%(db_charset)s'

	DB_CONNECT_PARAMS = _db_connect_params % _db_config

	#DB_CONNECT_PARAMS='mysql+mysqldb://root:root@localhost/account?charset=utf8'
	u'''
	:param pool_size=5: the number of connections to keep open
	inside the connection pool. This used with
	:class:`~sqlalchemy.pool.QueuePool` as
	well as :class:`~sqlalchemy.pool.SingletonThreadPool`. With
	:class:`~sqlalchemy.pool.QueuePool`, a ``pool_size`` setting
	of 0 indicates no limit; to disable pooling, set ``poolclass`` to
	:class:`~sqlalchemy.pool.NullPool` instead.

	:param pool_recycle=-1: this setting causes the pool to recycle
	connections after the given number of seconds has passed. It
	defaults to -1, or no timeout. For example, setting to 3600
	means connections will be recycled after one hour. Note that
	MySQL in particular will disconnect automatically if no
	activity is detected on a connection for eight hours (although
	this is configurable with the MySQLDB connection itself and the
	server configuration as well).
	'''
	engine = create_engine(DB_CONNECT_PARAMS, echo=True, pool_size=10, pool_recycle=3600)

	Session = sessionmaker(bind=engine)
	ScopedSession = scoped_session(sessionmaker(bind=engine))


	def get_session():
	return ScopedSession()


	def get_no_scoped_session():
	return Session()

	#DBSession = get_session()

	BaseModel = declarative_base(bind=engine)

	#BaseModel.objects = DBSession.query_property() # all model will have it
	BaseModel.__table_args__ = { # 指定所有model的默认参数
	u'mysql_charset': u'utf8',
	u'mysql_engine': u'InnoDB'
	}


	def create_tables():
	BaseModel.metadata.create_all(engine)


	def drop_tables():
	BaseModel.metadata.drop_all(engine)


	u'''
	学生成绩管理系统

	班级表

	学生表

	科目表

	成绩表

	涉及操作:
	添加/修改/删除班级
	添加/修改/删除学生
	添加/修改/删除科目
	添加/修改/删除学生成绩

	'''


	class MClass(BaseModel):
	__tablename__ = u'mclass' #数据库表名称

	id = Column(u'id', INTEGER, primary_key=True) #班级ID
	name = Column(u'name', VARCHAR(50), unique=True, nullable=False) #班级名称,唯一且不能为空
	created = Column(u'created', DATETIME, default=datetime.now)

	def __repr__(self):
	return u'<Class %s with %d students, created at %s>' % (
	self.name, len(self.students), self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


	class MStudent(BaseModel):
	__tablename__ = u'mstudent'

	id = Column(u'id', INTEGER, primary_key=True) #学生ID
	class_id = Column(u'class_id', ForeignKey(MClass.id), nullable=False) #学生所属班级ID
	name = Column(u'name', VARCHAR(30), nullable=False) #学生名称,必填
	age = Column(u'age', INTEGER) #学生年龄，选填
	created = Column(u'created', DATETIME, default=datetime.now)

	cls = relationship(MClass, backref=backref(u'students', cascade=u'all')) #学生所属班级对象

	def __repr__(self):
	return u'<Student %s in Class %s, created at %s>' % (
	self.name, self.cls.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


	class MCourse(BaseModel):
	__tablename__ = u'mcourse'

	id = Column(u'id', INTEGER, primary_key=True) #课程ID
	name = Column(u'name', VARCHAR(30), unique=True, nullable=False) #课程名称,唯一且非空
	created = Column(u'created', DATETIME, default=datetime.now)

	def __repr__(self):
	return u'<Course %s, created at %s>' % (self.name, self.created.strftime(u'%Y-%m-%d %H:%M:%S'))


	class MScore(BaseModel):
	__tablename__ = u'mscore'

	id = Column(u'id', INTEGER, primary_key=True) #成绩记录ID
	student_id = Column(u'student_id', ForeignKey(MStudent.id), nullable=False) #学生ID
	course_id = Column(u'course_id', ForeignKey(MCourse.id), nullable=False) #课程ID
	score = Column(u'score', FLOAT, default=0.0)

	student = relationship(MStudent, backref=backref(u'scores', cascade=u'all'))
	course = relationship(MCourse, backref=backref(u'scores', cascade=u'all'))

	def __repr__(self):
	return u'<Student %s in Class %s with %.1f for Course %s, created at %s>' % (
	self.student.name, self.student.cls.name, self.score, self.course.name,
	self.created.strftime(u'%Y-%m-%d %H:%M:%S')
	)


	cls = MClass
	stu = MStudent
	c = MCourse
	s = MScore


	class RandomException(Exception):
	pass


	def random_exception():
	if random.random() < 0.0000005:
	raise RandomException()


	def random_age():
	return random.randint(20, 30)


	def random_score():
	return round(random.random() * 100, 1)


	def init_data():
	session = get_session()
	try:
	course_names = [u'语文', u'数学', u'英语']
	courses = []
	# 创建3门课程
	for course_name in course_names:
	course = MCourse()
	course.name = course_name
	random_exception()
	session.add(course)
	courses.append(course)

	# 随机创建3个班级
	for cls_index in range(3):
	# create a class
	cls = MClass()
	cls.name = u'class-%d' % (cls_index + 1, )
	random_exception()

	# 为每个班级随机创建10个学生
	for stu_index in range(10):
	student = MStudent()
	student.name = u'class-%d-student-%d' % (cls_index + 1, stu_index + 1)
	student.age = random_age()
	random_exception()

	# 为每个班级中的学生随机生成每门课程的成绩
	for course in courses:
	score = MScore()
	score.score = random_score()
	score.student = student
	score.course = course
	random_exception()
	#session.add(score)

	#session.add(student)
	cls.students.append(student)

	session.add(cls)

	session.commit()
	return True
	except RandomException:
	print u'random exception happened, rollback all transaction'
	session.rollback()
	finally:
	session.close()
	return False


	def random_delete_class():
	session = get_session()
	classes = session.query(MClass).all()
	cls = random.choice(classes)
	print u'will delete class %s with id %d' % (cls.name, cls.id)
	session.delete(cls)
	session.commit()


	def random_delete_student():
	session = get_session()
	students = session.query(MStudent).all()
	stu = random.choice(students)
	print u'will delete student %s with id %d' % (stu.name, stu.id)
	session.delete(stu)
	session.commit()


	def random_delete_course():
	session = get_session()
	courses = session.query(MCourse).all()
	course = random.choice(courses)
	print u'will delete course %s with id %d' % (course.name, course.id)
	session.delete(course)
	session.commit()


	def main():
	# 删除所有的表
	print u'dropping tables ...'
	drop_tables()
	# 创建所有的表
	print u'creating tables ...'
	create_tables()
	# 初始化数据
	print u'init database records ...'
	init_success = init_data()
	if init_success:
	# 随机操作数据
	print u'random delete class ...', u'' 50
	random_delete_class()
	print u'random delete student', u'' 50
	random_delete_student()
	print u'random delete course', u'' 50
	random_delete_course()


	if __name__ == u'__main__':
	main()